Drive device for electric vehicle

ABSTRACT

A drive device for an electric vehicle in which, by improving a supporting structure of an input shaft of a speed reduction unit, the bearing stiffness of a hub bearing is improved, while the rotational accuracy and the durability of an input shaft of a speed reduction unit are improved and noise is suppressed. The drive device includes: a speed reduction unit including an input shaft driven by an electric motor; a hub unit rotationally driven by the speed reduction unit; and a housing. The input shaft of the speed reduction unit is supported by bearings provided at two locations in the axial direction. The bearings are both supported by the output member, and the PCD of the inboard-side hub bearing of the hub bearings disposed at the two locations in the axial direction of the hub unit is larger than the PCD of the outboard-side hub bearing.

TECHNICAL FIELD

The present invention relates to a drive device for an electric vehicle including an electric motor as a drive source, and particularly to a drive device for an electric vehicle of an in-wheel motor type.

BACKGROUND ART

A conventionally known drive device for an electric vehicle of an in-wheel motor type is made up of an electric motor, a speed reduction unit to which the output of the electric motor is inputted, and a hub unit which is rotationally driven by the speed-reduced output of the speed reduction unit (Patent Literature 1).

In the drive device for an electric vehicle disclosed in Patent Literature 1, an electric motor is disposed outside the speed reduction unit in the radial direction, and the speed reduction unit in which planetary gear-type units are disposed in two stages in the axial direction is used.

The input shaft of the speed reduction unit is supported by hub bearings constituted by bearings disposed at two locations in the axial direction. Of these bearings, the inboard-side bearing is attached to a housing of the speed reduction unit, and the outboard-side bearing is attached to the output member of the speed reduction unit. The housing is supported by the vehicle body via the suspension, and the output member is coupled and integrated with an inner member of the hub unit to rotationally drive the vehicle wheel.

In the drive device for an electric vehicle of the above-described configuration, the radial load acting on the input shaft of the speed reduction unit is supported by the housing via the inboard-side bearing on the inboard side, and is supported by the output member of the speed reduction unit via the outboard-side bearing on the outboard side.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Laid-Open No. 2001-32888

SUMMARY OF INVENTION Technical Problem

Regarding the supporting structure of the input shaft of the speed reduction unit, while vibration and impact associated with the rotation of the vehicle wheel are transmitted to the end portion of the input shaft on the outboard side via the outboard-side bearing, the end portion on the inboard side is supported by a stationary housing via the inboard-side bearing.

In the above described shaft supporting structure, problems exist in that eccentric load is likely to act on the inboard-side bearing and the outboard-side bearing due to the effect of elastic deformation of the hub and the hub bearings when the vehicle wheel is subjected to load, thereby causing a decline of the rotational accuracy of the input shaft, a deterioration of the durability of the bearings, and an occurrence of the rotation noise of the bearings.

Accordingly, it is an object of the present invention to provide a drive device for an electric vehicle in which, by improving the supporting structure of the input shaft of the speed reduction unit, the bearing stiffness of the hub bearings is improved, while the rotational accuracy and the durability of the input shaft of the speed reduction unit are improved and noise is suppressed.

Solution to Problem

To solve the above described problems, the present invention provides a drive device for an electric vehicle, comprising: an electric motor; a speed reduction unit including an input shaft driven by output of the electric motor; a hub unit rotationally driven by an output member of the speed reduction unit; and a housing accommodating the electric motor and the speed reduction unit, wherein the input shaft of the speed reduction unit is supported by bearings provided at two locations in the axial direction, the drive device being configured such that the bearings provided at the two locations are both supported by the above described output member, and a PCD (pitch circle diameter) of the inboard-side hub bearing of the hub bearings disposed at the two locations in the axial direction of the hub unit is set to be larger than the PCD of the outboard-side hub bearing.

According to the above-described configuration, since the bearings for supporting the input shaft at two locations in the axial direction are attached together to the output member, vibration and impact transmitted from the vehicle wheel to the output member will be imposed on both the bearings at the same time and in the same manner. For this reason, both the bearings are prevented from being subjected to eccentric load, and the bearing stiffness of either of the hub bearings is improved compared with one having the same PCD.

The output member may be configured to include flanges disposed on both sides in the axial direction of a speed reduction rotational member such as a pinion gear so that the flanges are coupled and integrated with each other by both end portions of a support pin of the speed reduction rotational member being secured to the flanges, and each of the above-described bearings is placed between the inner radial surface of each flange and the input shaft.

The above-described “speed reduction rotational member” and “support pin” correspond to the “pinion gear” and the “pinion pin” respectively in the case of a planetary gear type. By attaching each bearing to the inner radial surface of each of the above-described flanges, it is possible to realize a configuration in which both bearings are attached together to the output member.

Since the above-described speed reduction unit has a configuration in which the flanges on both sides are coupled and integrated with each other by support pins, the pinion gear can be placed between both the flanges.

Thus, the flanges can be configured to be coupled with each other by a bridge so that the flanges can be securely coupled and integrated with each other by the bridge.

Since both the flanges are securely engaged and integrated with each other by the above-described bridge, the support stiffness of the support pin such as the pinion pin whose both end portions are coupled to both the flanges is increased. Moreover, by providing the bridge at multiple locations of equally spaced positions in a circumferential direction of the flange, the rotation of the output member becomes smooth, and the rotational accuracy of the input shaft and the rotor of the electric motor fitted and secured to the input shaft is improved.

Advantageous Effects of Invention

As described so far, since the present invention is configured such that a pair of bearings for supporting the input shaft of the speed reduction unit are both attached to the output member of the speed reduction unit, the concerned bearings are prevented from being subjected to eccentric load. As a result of this, the present invention has the effects of improving the rotational accuracy of the input shaft and the durability of the bearings, and further suppressing the rotation noise of the bearings. It also has an effect of improving the bearing stiffness of the hub bearings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view of Embodiment 1.

FIG. 2 is a partially enlarged cross sectional view of Embodiment 1.

FIG. 3 is an enlarged sectional view taken in X1-X1 line in FIG. 2.

FIG. 4 is a perspective view of a spacer shown in FIG. 3.

FIG. 5 is a cross sectional view taken in X2-X2 line in FIG. 1.

FIG. 6A is a cross sectional view of a variant of a speed reduction unit portion.

FIG. 6B is a cross sectional view taken in X3-X3 line of FIG. 6A.

FIG. 7 is a cross sectional view to show a part of Embodiment 2.

FIG. 8 is a cross sectional view of Embodiment 3.

FIG. 9 is a side view of Embodiment 3.

FIG. 10 is a partial cross sectional view of a variant of Embodiment 3.

DESCRIPTION OF EMBODIMENTS

Hereafter, embodiments of the present invention will be described based on the appended drawings.

Embodiment 1

A drive device for an electric vehicle relating Embodiment 1 includes, as principal components, an electric motor 11, a speed reduction unit 12 which is driven by the output power of the electric motor 11, a hub unit 15 which is rotated by an output member 14 coaxial with an input shaft 13 of the speed reduction unit 12, and a housing 16 which accommodates the electric motor 11 and the speed reduction unit 12, as shown in FIG. 1.

The above-described housing 16 includes a cylindrical portion 17 and a front end portion 18 in the radial direction, which is provided at the front end of the cylindrical portion (the end portion of an outboard side, or an end portion on the left side of the figure). A central portion of the front end portion 18 is opened, and a rear end portion of an outer member 21 of the hub unit 15 is fitted into an opening hole 19 so that a flange 22 is secured to the front end portion 18 with a bolt 23.

A partition base portion 18 a, which is concentric with the opening hole 19 and has a larger diameter than that, is provided inside the front end portion 18 of the housing 16. A dish-shaped partition member 20 is secured to the partition base portion 18 a with a bolt 20 a. A center hole 25 is provided at the center of the partition member 20. The center hole 25 faces an outer radial surface of the input shaft 13 with a gap in a radial direction therebetween. A partition 24 is formed of the above-described partition base portion 18 a and the partition member 20 joined and secured thereto. The partition 24 has a function of sectioning the interior of the housing 16 into an accommodation space for the electric motor 11 on the outer radial side, and an accommodation space for the speed reduction unit 12 on the inner radial side.

A suspension joining portion 27 which projects in the axial direction is provided at two centrosymmetric locations on a rear end edge of the cylindrical portion 17 of the housing 16. In a conventional automobile, the hub unit 15 is joined to the suspension with a knuckle of the vehicle body lying therebetween; however, in the present Embodiment 1, the suspension on the vehicle body side can be directly joined to the suspension joining portion 27 which is a part of the housing 16.

Since the housing 16 will achieve the function of the knuckle, it can be described as a structure in which the knuckle is integrated with the housing 16. In this case, if the outer member 21 of the hub unit 15 becomes necessary to be replaced, the replacement can be performed simply by detaching the bolt 23 without need of detaching the housing 16 from the suspension.

In the case shown in the figure, the electric motor 11 is a radial-gap-type brushless DC motor, and is made up of a stator 28 secured to an inner radial surface of the cylindrical portion 17 of the housing 16, and a rotor 29 disposed on an inner radial surface of the stator 28 with a radial gap. The rotor 29 is fitted and secured to the input shaft 13 by a rotor support member 31.

The rotor support member 31 is made up of a support member cylindrical portion 31 a (see FIG. 2) fitted to an inner radial portion of the rotor 29, and a support member disc portion 31 b which extends reward along the partition 24 and which is bent to the inner radial direction of the partition. A boss portion 31 c is provided in an inner radial portion of the support member disc portion 31 b, and the boss portion 31 c is fitted to the input shaft 13 and secured to the input shaft 13 with a key locking portion 35.

The above-described boss portion 31 c is inserted into the inner radial side of the center hole 25 of the partition 24, and an oil seal member 36 is placed between the center hole 25 and the boss portion 31 c (see FIG. 2). The accommodation portion of the electric motor 11 and the accommodation portion of the speed reduction unit 12 are partitioned and oil-sealed by the partition 24 and the oil seal member 36. As a result of this, lubricant oil on the speed reduction unit 12 side is prevented from moving to the electric motor 11 side, and thus the electric motor 11 side is kept dry, thus resolving the malfunction that the lubricant oil hinders the rotation of the rotor 29.

The speed reduction unit 12 is of a planetary gear type, and is made up of, as shown in FIG. 2, the input shaft 13, the output member 14, a sun gear 39 which is attached to the outer radial surface of the input shaft with a key locking portion 38, a ring gear 42 which is disposed along an inner radial surface of a partition cylindrical portion 24 b in the outer periphery of the sun gear 39, and which is attached with a key locking portion 41, and pinion gears 43 which are disposed at three locations equally spaced in the circumferential direction between the ring gear 42 and the sun gear 39. The pinion gear 43 is supported by a pinion pin 45 via a needle roller bearing 44.

The output member 14 includes a coupled shaft portion 47 at an end portion of an outboard side thereof. The coupled shaft portion 47 is spline-coupled to an inner member 46 of the hub unit 15 and secured by a nut 50. A bearing support portion 49, which is formed to have a one-step larger diameter than that of the coupled shaft portion 47, is provided on the inner end side of the coupled shaft portion 47.

On an inboard side of the output member 14, a pair of flanges 52 and 53 which oppose each other in the axial direction are provided with a spacing slightly larger than the width of the pinion gear 43 in the axial direction. A bridge 54 for joining the flanges 52 and 53 to each other in the axial direction is provided at three locations of equally spaced positions in the circumferential direction. The flanges 52 and 53 have a function as a carrier in the speed reduction unit 12 of planetary gear type.

Providing a bridge 54 at equally spaced positions in the circumferential direction allows the output member 14 to be smoothly rotated, and moreover, to improve the rotational accuracy of the rotor 29 of the electric motor 11 through the output member 14 and the input shaft 13.

A shaft hole 51 which is coaxial with the coupled shaft portion 47 is provided at the center of an end surface of the flange 53 of the inboard side. This shaft hole 51 has a length reaching the bearing support portion 49.

There are provided pinion gear accommodation portions 55 at the three locations, which are sectioned in the circumferential direction by the pair of the flanges 52 and 53 opposing each other in the axial direction, and the bridges 54 at the three locations in the circumferential direction (see FIG. 3). The pinion gear 43 is accommodated in each pinion gear accommodation portion 55, and both end portions of the pinion pin 45 are inserted through the flanges 52 and 53, respectively, and each secured by a locking screw 56. It can be said that both the flanges 52 and 53 are coupled and integrated with each other not only by the bridge 54, but also by the pinion pin 45.

Since the flanges 52 and 53 are integrated with each other by the bridge 54, the support stiffness at both ends of the pinion pin 45 increases.

A thrust plate 57 is placed between each side surface of each pinion gear 43 and each of the flanges 52 and 53 to ensure smooth rotation of the pinion gear 43.

A pair of rolling bearings 58 and 59 for supporting the input shaft 13 is provided on both sides of the sun gear 39 between an inner radial surface of each of the flanges 52 and 53 and the outer radial surface of the input shaft 13 opposing each of the inner radial surfaces of the flanges 52 and 53. By adopting this configuration, the respective rolling bearings 58 and 59 are supported together by the same output member 14.

Further, as shown in FIG. 2, the positional relationship in the axial direction between each of the rolling bearings 58 and 59, and a fitting portion between the support member disc portion 31 b and the input shaft 13 is such that the respective rolling bearings 58 and 59 are disposed together on the outboard side, and form a so-called cantilever support structure as the support structure for the input shaft 13.

In contrast to this, in the conventional art (Patent Literature 1), while the bearing on the outboard side is disposed on the outboard side with respect to the fitting portion between the support member disc portion and the input shaft, the bearing on the inboard side is attached to the housing, and therefore is located on the inboard side with respect to the above-described fitting portion. Therefore, the support structure of the input shaft forms a so-called both-end support structure. The cantilever support structure is characterized by a simplified structure compared with the both-end support structure.

The above-described rolling bearing 58 on the outboard side is configured such that its inner ring is engaged with a stepped portion 61 provided in the input shaft 13, and its outer ring is engaged with a stepped portion 62 provided in an inner radial surface of the shaft hole 51. The rolling bearing 59 on the inboard side is configured such that its inner ring is engaged with the boss portion 31 c of the rotor support member 31 and the key locking portion 35, and its outer ring is engaged with a retaining ring 63.

The sun gear 39 is placed between the respective inner rings of the respective rolling bearings 58 and 59, and also a spacer 64 is placed between the outer rings. The spacer 64 prevents both the rolling bearings 58 and 59 from being displaced in a direction to approach to each other.

The spacer 64 is formed into a cylindrical form as shown in FIGS. 3 and 4, and is provided, at three locations in the circumferential direction, with window holes 65 which correspond to the shape of the above-described pinion gear accommodation portion 55. Further, a closure portion 66 between the respective window holes 65 is formed into a shape corresponding to the shape of the bottom plane of the above-described bridge 54. The spacer 64 is placed between the rolling bearings 58 and 59 on the inner radial surface of the shaft hole 51 in a posture that each window hole 65 corresponds to the pinion gear accommodation portion 55 (see FIG. 3), and is configured to be positioned by screwing a securing screw 67 from an outer radial surface of the bridge 54 into a positioning hole 60 (see FIG. 4).

The above-described spacer 64 allows to control the bearing pressurization to be applied to both the rolling bearings 58 and 59 by appropriately setting the axial length thereof, thus providing a simple fixed-position pressurization structure.

When seen in the radial direction, the speed reduction unit 12 is radially disposed to be accommodated on the inner radial side of the electric motor 11 with respect to the partition 24, and the size in the axial direction is made compact compared with a case where the unit is disposed in the axial direction.

Here, additionally describing the partition 24, the partition cylindrical portion 24 b is placed between the electric motor 11 and the speed reduction unit 12, which are disposed in the radial direction, and the partition disc portion 24 a is placed between the speed reduction unit 12 and the support member disc portion 31 b. A peripheral edge portion of the center hole 25 faces the outer radial surface of the boss portion 31 c of the rotor support member 31 with a predetermined spacing therebetween. The ring gear 42 of the speed reduction unit 12 is secured to an inner radial surface of the partition base portion 18 a with the key locking portion 41.

The oil seal member 36 is placed between the peripheral edge portion of the above-described center hole 25 and the boss portion 31 c. The accommodation space for the electric motor 11 of the housing 16 and the accommodation space for the speed reduction unit 12 are partitioned by the presence of the oil seal member 36 and the partition 24. Since, as a result of this, the lubricant oil on the speed reduction unit 12 side is prevented from moving to the electric motor 11 side, and thus the electric motor side is kept dry, the lubricant oil is prevented from hindering the rotation of the rotor 29.

Although, it is described above that both the flanges 52 and 53 of the output member 14 are coupled and integrated by both the bridge 54 and the pinion pin 45, it is possible to take a structure in which the flange 53 is configured to be a separate body from the output member 14 and both are coupled and integrated by the pinion pin 45, as shown in FIGS. 6A and 6B.

An oil filler port 68 and an oil drainage port 69 for lubricant oil to lubricate the interior of the speed reduction unit 12 are provided in the front end portion of the housing 16. The lubricant oil is sealed by the above-described oil seal member 36 on the electric motor 11 side, and is sealed by an oil seal member 70, which is placed between the bearing support portion 49 of the output member 14 and the outer member 21, on the hub unit 15 side. The oil filler port 68 and the oil drainage port 69 are blocked by a blocking screw 72.

Since the electric motor 11 and the speed reduction unit 12, excepting the rear end portion (the end portion of the inboard side) of the input shaft 13, fit in the range of the axial length of the cylindrical portion 17 of the housing 16 as shown in FIG. 1, a rear cover 73 is fitted to the rear end portion of the cylindrical portion 17 via a seal member 60. A fin 74 for heat dissipation is provided on an outer side surface of the rear cover 73 so that heat of the electric motor 11 is dissipated to the outside.

A rotation angle sensor 75 is provided between the center hole of the rear cover 73 and the input shaft 13 that passes through the center hole, and that portion is covered by a sensor cover 77. The rotation angle sensor 75 shown is a resolver, and whose sensor stator 75 a is secured into the center hole of the rear cover 73, and the sensor rotor 75 b is attached to the input shaft 13.

A lead wire 83 of the sensor stator 75 a is connected to a connector insertion portion 78 provided outside the sensor cover 77. As the rotation angle sensor 75, a Hall element can be used besides the above-described resolver.

A rotational angle of the input shaft 13 detected by the rotation angle sensor 75 is inputted to a control circuit, which is omitted from showing, via the above-described signal wire cable to be used for the rotational control of the electric motor 11.

A power supply terminal box 76 for providing power supply to the stator 28 of the electric motor 11 is provided at a position decentered toward an outer peripheral edge of the above-described rear cover 73, and at a position 90 degrees different from the above-described suspension joining portion 27 (see FIG. 5).

The power supply terminal box 76 is formed into a cylindrical shape that passes through the rear cover 73, and is provided with a working hole 80 in an outer peripheral portion of the box. The working hole 80 is usually blocked by a cover 81. A power supply terminal 82 is provided inside the box at a position opposing the working hole 80. A lead wire 83 connected to the winding of the stator 28 is connected to the power supply terminal 82, and also a connection terminal of a power supply cable 84 is connected to the same power supply terminal 82. These are secured by fastening screws 85. A cable hole 84 a is provided at a rear end of the power supply terminal box 76 and the power supply cable 84 is inserted therethrough.

The hub unit 15 is made up of, as shown in FIG. 1, the above-described inner member 46 which is integrated with a hub 86, a pair of inner rings 87 that are fitted to an outer radial surface of the inner member 46, the outer member 21 having the flange 22, an outer ring 88 fitted to an inner radial surface of the outer member 21 and having multiple rows of tracks, and multiple rows of balls 89 to be placed between the inner ring 87 and the outer ring 88. The vehicle wheel is attached to the hub 86 with hub bolts 90.

The coupled shaft portion 47 of the output member 14 is spline-coupled to an inner radial surface of the inner member 46, and a tip end portion of the coupled shaft portion 47 projecting to the outside from the inner member 46 is secured by the nut 50 as described above. In place of the securing means using the nut 50, securing means such as press cut joint, diameter expansion caulking, and swing caulking may be adopted.

Although the above-described hub unit 15 is of a form of so-called first generation, those of a form of the second generation or third generation may be used.

The driving device for an electric vehicle of Embodiment 1 is configured as described above, and next, the operation thereof will be described.

When the electric motor 11 is driven by an accelerator at the driving seat being activated, the input shaft 13 is rotated integrally with the rotation of the rotor 29, and a motor output is inputted to the speed reduction unit 12. In the speed reduction unit 12, when the sun gear 39 rotates integrally with the input shaft 13, the pinion gears 43 revolve around the sun gear 39 while rotating on their own axes. Each of the pinion pins 45 performs speed-reduced rotation at its revolving speed, and thereby rotates the output member 14 at a speed-reduced output shown by the above-described speed reduction ratio.

The inner member 46 of the hub unit 15 is rotated integrally with the coupled shaft portion 47 of the output member 14, thereby driving the wheel attached to the hub 86.

The above-described input shaft 13 rotates by being supported respectively by the rolling bearing 58 on the outboard side and the rolling bearing 59 on the inboard side at both sides of the pinion gear 43. Since these rolling bearings 58 and 59 are both attached to the respective flanges 52 and 53 (respective flanges 52 and 53 which are integrated via the pinion pin 45 in the case of FIGS. 6A and 6B) which are each integrated with the output member 14, vibration and impact in the radial direction which are transmitted from the wheel to the output member 14 through the hub unit 15 is imposed onto both the rolling bearings 58 and 59 at the same time and in the same manner.

Since, as a result of that, both the rolling bearings 58 and 59 can be prevented from being subjected to eccentric load, it is possible to improve the rotational accuracy and durability, and suppress the rotation noise.

Since the pinion pin 45 of the pinion gear 43 is supported at both end portions thereof by the respective flanges 52 and 53, the support stiffness increases compared with a conventional case where it is cantilevered.

The above-described rolling bearings 58 and 59 are disposed on the outboard side with respect to the fitting portion between the rotor support member 31 of the rotor 29 and the input shaft 13, that is, the key locking portion 35, so that the support structure becomes simple and easy to be assembled compared with a conventional case where the bearings are disposed on both sides thereof.

Further, since the lubricant oil in the speed reduction unit 12 is sealed on the electric motor 11 side by the oil seal member 36, and sealed on the hub unit 15 side by the oil seal member 70, leakage on the electric motor 11 side and the hub unit side is prevented. As a result of that, on the electric motor 11 side, rotation of the rotor 29 is not hindered, and on the hub unit 15 side, leakage of the lubricant oil to the outside through the hub unit 15 is prevented.

The heat generated in association with the driving of the electric motor 11 is effectively dissipated by the fin 74 of the rear cover 73.

The rotational angle of the input shaft 13, which is necessary for the rotational control of the electric motor 11, is detected by the rotation angle sensor 75 and inputted to the control apparatus.

Embodiment 2

Embodiment 2 shown in FIG. 7 differs in the configuration of the hub unit 15 compared with the above-described Embodiment 1. That is, the flange 22 of the outer member 21 of the hub unit 15 in this case is formed to have a larger diameter than that of the flange 22 (see FIG. 1) of the above-described Embodiment 1.

A flange cylindrical portion 32 projecting in the axial direction is provided in the inner side surface of the flange 22 with a larger diameter. The flange cylindrical portion 32 extends over an outer radial surface of the flange 53 on the outboard side of the output member 14. The flange cylindrical portion 32 is fitted to an inner radial surface of the opening hole 19 of the front end portion 18 of the housing 16.

Since, compared with the case of Embodiment 1, the opening hole 19 is formed to have a large inner diameter, it is easy to fabricate the partition 24 which is integrated with the front end portion 18, in the case of this Embodiment 2. For this reason, in the case of Embodiment 2, the partition member 20 (see FIG. 1) which is a separate member is not used.

A ball of a hub bearing 89 a on the outboard side is placed between a track groove formed in the outer radial surface of the inner member 46, and a track groove formed in the inner radial surface of the outer member 21. Moreover, the ball of the hub bearing 89 b on the inboard side is placed between a track surface formed in the outer radial surface of the flange 52 and a track groove formed in an inner radial surface of the flange cylindrical portion 32.

Letting the radii from “the center” of the ball center of the hub bearing 89 a on the outboard side, the center of the pinion shaft 45, and the ball center of the hub bearing 89 b on the inboard side be r1, r2, and r3, respectively, these sizes have a relationship as r1<r3, and r2<r3. Other configurations are the same as those of the case of Embodiment 1.

As describe above, setting the ball PCD of the hub bearing 89 b on the inboard side to be larger than the ball PCD of the hub bearing 89 a on the outboard side results in increasing in the bearing stiffness of the hub unit 15. Where, the term “PCD” indicates twice the radius from the center of the ball.

It is noted that the hub unit 15 in this case can be said to be a variant form of the so-called third generation.

Although, in the illustrated case, each of the balls of the hub bearings 89 a and 89 b is configured to be in direct contact with the track groove, it is also possible to configure such that a bearing in which the track groove is provided in each of its inner ring and outer rings is used, and these track rings are fitted to the aforementioned opposite members.

Embodiment 3

Embodiment 3 shown in FIGS. 8 to 10 differs from Embodiment 1 in the configurations of the hub unit 15, the rotation angle sensor 75, the power supply terminal box 76, and the connector insertion portion 78.

That is, the hub unit 15 in this case is formed such that the flange 22 of the outer member 21 has a larger diameter than in the case of Embodiment 1. For this reason, there is no need of adopting a partition base portion 18 a as in Embodiment 1, and the single housing 16 is used. The flange 22 with a larger diameter is secured to the housing 16 with the bolt 23.

The ball 89 a on the outboard side constituting the hub bearing is placed between the track groove provided in the outer radial surface of the inner member 46 and the track groove provided in the inner radial surface of the outer member 21. Further, the ball 89 b on the inboard side is placed between the track groove provided in the outer radial surface of the output member 14 and the track groove provided in the inner radial surface of the outer member 21. It can be said to be a variant type of the so-called third-generation.

The rotation angle sensor 75 is provided between opposite surfaces in the axial direction of the support member disc portion 31 b of the rotor support member 31, and the partition disc portion 24 a. A sensor rotor 91 a is made up of a magnet which is attached to the support member disc portion 31 b with a vis 92. Moreover, a sensor stator 91 b is made up of a Hall element attached to the opposite surface of the partition disc portion 24 a with a vis 93. Both oppose each other via an axial gap.

As shown in FIG. 10, the cross sectional shape of the sensor rotor 91 b may be formed into a reverse L-shape, and a radial gap may be formed between the horizontal portion of the sensor rotor 91 b and the sensor stator 91 a.

The power supply terminal box 76 and the connector insertion portion 78 are both provided in the housing 16 (see FIG. 9). The power supply terminal box 76 is configured such that an accommodation recessed portion 94 is provided within the range of the wall thickness of a rear end surface of the housing 16, and the power supply terminal 82 is provided inside the accommodation recessed portion 94. A communication hole 95 in communication with the interior of the housing 16 is provided in a deep part of the accommodation recessed portion 94. The opening surface of the accommodation recessed portion 94 is blocked by a cover member 96. The cover member 96 is provided with a cable hole 97 for passing the power supply cable 84.

Further, the working hole 80 is provided in the wall surface of the housing 16. This working hole 80 is usually blocked by the cover 81. The lead wire 83 on the electric motor 11 side is connected to the power supply terminal 82 through the communication hole 95, and the power supply cable 84 is drawn in through the cable hole 97 so that its connection terminal is connected to the power supply terminal 82. Both are coupled to the power supply terminal 82 with a fastening screw 85.

The connector insertion portion 78 is provided in the rear end surface of the housing 16 side-by-side with the power supply terminal box 76, as shown in FIG. 9. The connector insertion portion 78 is configured such that a recessed portion 99 is provided in the rear end surface of the housing 16, and a lead wire hole 100 which brings a deep part of the recessed portion 99 and the interior of the housing 16 into communication is provided (see FIG. 8). A lead wire 101 of the rotation angle sensor 75 is connected to the interior of the recessed portion 99 through the lead wire hole 100. The connector (not shown) of the signal cable is inserted into the connector insertion portion 78.

As described above, the configuration in which both the power supply terminal box 76 and the connector insertion portion 78 are provided in the housing 16 can simplify the configuration of the rear cover 73 so that it can be made up of a thin metal plate, a plastic plate, and the like.

REFERENCE SIGNS LIST

-   11 Electric motor -   12 Speed reduction unit -   13 Input shaft -   14 Output member -   15 Hub unit -   16 Housing -   17 Cylindrical portion -   18 Front end portion -   18 a Partition base portion -   19 Opening hole -   20 Partition member -   20 a Bolt -   21 Outer member -   22 Flange -   23 Bolt -   24 Partition -   24 a Partition disc portion -   24 b Partition cylindrical portion -   25 Center hole -   26 Fin -   27 Suspension joining portion -   28 Stator -   29 Rotor -   31 Rotor support member -   31 a Support member cylindrical portion -   31 b Support member disc portion -   31 c Boss portion -   32 Flange cylindrical portion -   35 Key locking portion -   36 Oil seal member -   38 Key locking portion -   39 Sun gear -   41 Key locking portion -   42 Ring gear -   43 Pinion gear -   44 Needle roller bearing -   45 Pinion pin -   46 Inner member -   47 Coupled shaft portion -   48 Rolling bearing -   49 Bearing support portion -   50 Nut -   51 Shaft hole -   52, 53 Flange -   54 Bridge -   55 Pinion gear accommodation portion -   56 Locking screw -   57 Thrust plate -   58, 59 Rolling bearing -   60 Positioning hole -   61, 62 Stepped portion -   63 Retaining ring -   64 Spacer -   65 Window hole -   66 Closure portion -   67 Securing screw -   68 Oil filler port -   69 Oil drainage port -   70 Oil seal member -   71 Groove -   72 Blocking screw -   73 Rear cover -   74 Fin -   75 Rotation angle sensor -   75 a Sensor stator -   75 b Sensor rotor -   76 Power supply terminal box -   76 a Power supply terminal -   77 Sensor cover -   78 Connector insertion portion -   79 Insertion hole -   80 Working hole -   81 Cover -   82 Power supply terminal -   83 Lead wire -   84 Power supply cable -   84 a Cable hole -   85 Fastening screw -   86 Hub -   87 Inner ring -   88 Outer ring -   89 Ball -   89 a, 89 b Hub bearing -   90 Hub bolt -   91 a Sensor rotor -   91 b Sensor stator -   92, 93 Vis -   94 Accommodation recessed portion -   95 Communication hole -   96 Cover member -   97 Cable hole -   99 Recessed portion -   100 Lead wire hole 

The invention claimed is:
 1. A drive device for an electric vehicle, comprising: an electric motor; a speed reduction unit including an input shaft and an output member, wherein the input shaft is driven by output of the electric motor, and the entire output member is rotatable; a hub unit rotationally driven by the output member of the speed reduction unit; a housing accommodating the electric motor and the speed reduction unit; plural input-shaft-support bearings, provided at plural locations, respectively, in the axial direction along the input shaft of the speed reduction unit, wherein the input-shaft-support bearings are supported by the output member of the speed reduction unit; and an inboard-side hub bearing and an outboard-side hub bearing, disposed at two locations, respectively, in the axial direction of the hub unit, wherein a pitch circle diameter of the inboard-side hub bearing is set to be larger than the pitch circle diameter of the outboard-side hub bearing.
 2. The drive device of an electric vehicle according to claim 1, wherein the outboard-side hub bearing is placed between an inner member and an outer member of the hub unit, and inboard-side hub bearing is placed between the output member and the outer member.
 3. The drive device for an electric vehicle according to claim 1, comprising a support structure in which the input-shaft-support bearings are disposed on an outboard side of a fitting portion between the input shaft and a rotor support member of the electric motor.
 4. The drive device for an electric vehicle according to claim 1, wherein the output member of the speed reduction unit has a pair of flanges which are disposed on both sides in an axial direction of a speed reduction rotational member of the speed reduction unit, the flanges are coupled and integrated with each other by both end portions of a support pin of the speed reduction rotational member being secured to each flange, and each of the input-shaft-support bearings is placed between an inner radial surface of each flange and the input shaft.
 5. The drive device for an electric vehicle according to claim 4, wherein the speed reduction unit is a planetary gear speed reduction unit which is made up of a sun gear and a ring gear, which are provided coaxially with the input shaft, a plurality of pinion gears which are provided at equally spaced positions in a circumferential direction between the sun gear and the ring gear, and a carrier for holding the pinion gears.
 6. The drive device for an electric vehicle according to claim 5, wherein when r1 is a radius from a center to a ball of the outboard-side hub bearing, r2 is a radius from the center to a pinion shaft of at least one of the pinion gears, and r3 is a radius from the center to a ball of the inboard-side hub bearing, a relationship exists in that r1<r3, and r2<r3.
 7. The drive device for an electric vehicle according to claim 5, wherein the speed reduction unit is a planetary gear speed reduction unit, and the flanges are integrated with each other by bridges provided at a required spacing in a circumferential direction, the pinion gears are accommodated between the respective bridges, and both end portions of the pinion pin are supported by the flanges, respectively.
 8. The drive device for an electric vehicle according to claim 7, wherein the input-shaft-support bearings are each made up of a rolling bearing; a ring-shaped spacer is placed between outer rings of the input-shaft-support bearings; the spacer is provided with a window hole in a portion which opposes the speed reduction rotational member for avoiding interference; and the spacer includes a positioning hole that is screwed into from an outer radial surface of one of the bridges.
 9. The drive device for an electric vehicle according to claim 1, wherein the speed reduction unit is disposed on an inner diameter side of the electric motor, and an accommodation space in the housing for the speed reduction unit and an accommodation space in the housing for the electric motor are sectioned by a partition provided in the housing.
 10. The drive device for an electric vehicle according to claim 9, wherein the partition is made up of a partition base portion which is provided in the housing, and a partition member which is joined and secured to the partition base portion.
 11. The drive device for an electric vehicle according to claim 9, wherein a stator of the electric motor is secured to the housing on an outer diameter side of the speed reduction unit, a rotor is disposed between the stator and the partition, and a support member of the rotor is fitted to and integrated with the input shaft.
 12. The drive device for an electric vehicle according to claim 1, wherein a flange of an outer member of the hub unit is secured to the housing accommodating the electric motor and the speed reduction unit. 